Cathodoluminescence and surface physical studies of polycrystalline BaTiO3

We have studied polycrystalline BaTiO3 by using cathodoluminescence (CL), s canning tunneling and electron microscopy (STM and SEM) and Auger electron spectroscopy. The main aim of the work was the characterization of the grai n boundaries of the polycrystalline material by STM which show up in the CL images with a distinct intensity difference compared to the surfaces of th e grains. In CL the grain boundary contrast is strongly dependent on the sa mple temperature. In the STM results the grain boundaries could be identifi ed at room temperature by the presence of dark lines with a width of only 1 0 nm which is much narrower than for the CL images (1 to 2 mu m in the latt er case). The origin of the contrast between grains and grain boundaries in the CL and STM images will be discussed.